1. Field of Invention
This invention relates to a method for management of semiconductor manufacturing equipment, and particularly to a method for managing semiconductor manufacturing equipment that performs different processes. This invention also relates to a system for managing semiconductor manufacturing lines including manufacturing equipment.
2. Description of Related Art
Semiconductor devices are manufactured by processing semiconductor substrates (wafers), which are usually grouped in lots, in a manufacturing line. The manufacturing line includes a plurality of manufacturing equipments to perform a plurality of processes.
In conventional semiconductor manufacturing lines, dedicated manufacturing equipment is assigned for each process to prevent cross-contamination between different processes. For example, a gate etching process for forming gate electrodes, and an active etching step for forming LOCOS (Local Oxidation of Silicon) structures, are respectively performed by dedicated etching equipment.
During plasma processes such as plasma etching, reaction products are produced in the plasma and are deposited within the processing chamber of the apparatus. Because different processes utilize different process gases and different plasma conditions, amounts and chemical compositions of the reaction products vary depending on the process. By assigning dedicated equipment to each process, it is possible to fix the compositions and rate of deposition of the reaction products within the chamber. Thereby, for instance, wet cleaning using various kinds of solvents, and maintenance for replacement parts can be performed at a fixed interval, e.g., after processing of predetermined number of wafers.
Thus, assigning dedicated equipment for each process enables planned maintenance, and accordingly, is more effective. Unfortunately, however, operating rates of different equipment cannot be equalized.
For example, gate etching equipment for etching polysilicon films can continuously process 5,000 wafers or more without wet cleaning. On the other hand, a shallow trench etching equipment for etching silicon substrates with an etching gas containing a high flow rate HBr gas requires a wet cleaning upon processing of 3,000 wafers or less. This is because shallow trench etching produces a large amount of reaction products within the etching chamber.
The difference in operation rates has led to a problem of increased costs due to ineffective equipment investment and increased personnel load for maintenance. Consequently, various methods and equipment for reducing amount of reaction products within processing chambers of manufacturing equipment have been proposed so as to improve the manufacturing efficiency.
Japanese Unexamined Patent Application Publication No. JP-A-11-214356 (first reference) discloses a dry etching method for forming trenches in a silicon substrate. According to the etching method disclosed in the first reference, the trenches are formed using a silicon nitride film pattern as an etching mask by performing the following steps in a single etching chamber. At first, a natural oxide film formed on the surface of the silicon substrate, on which trenches are to be formed, is removed using a fluorine-based etching gas, and then a silicon etching using a chlorine- or bromine-based etching gas is performed, thereby forming trenches in the silicon substrate.
According to this first reference, continuously performing plasma etching with a fluorine-based etching gas and then with a chlorine- or bromine-based etching gas in a single etching chamber markedly reduces the amount of reaction products deposited on the inner wall of the chamber. Thereby, the process may be performed with excellent repeatability, and consequently, the frequency of dry cleaning may be reduced.
U.S. Pat. No. 6,136,211 (second reference) discloses a method of cleaning an etching chamber while a substrate is being etched, or a self-cleaning etching process. With this etching method, a process gas including etchant gas is used to etch the substrate thereby depositing etch residue inside the chamber. Cleaning gas is added to the process gas for a sufficient time and in a volumetric flow ratio that is sufficiently high, to react with and remove substantially all the etch residue deposited by the process gas.
The etching methods disclosed in these references are both aimed at reducing the amount of reaction products in the etching chamber during a single process. These references are not intended to perform different processes in the production of semiconductor devices within a single etching chamber. For example, in the method of the first reference, the etching of natural oxide film and the etching of silicon substrate are both performed within a single etching chamber. However, the etchings of these different materials are performed during a single process of trench formation.
In addition, etching conditions disclosed in these references, which are optimized to reduce the reaction products, are not always suitable for realizing desirable etching properties such as, for instance, high processing accuracy.
On the other hand, different processes are sometimes needed to be performed in a same etching chamber due to, for instance, shortage of manufacturing equipment. In this case, it has been thought that cleaning of the chamber is required between different processes in order to prevent contamination by the reaction products deposited in another process (cross-contamination). Obviously, necessity of such cleaning between different processes reduces the manufacturing efficiency. Therefore, the use of a single chamber for different processes is not considered to be efficient or desirable.
Even if the methods of reducing the amount of residues proposed in the first and the second references are used, it is difficult to completely eliminate the deposition of reaction products in the chamber. Furthermore, such methods of reducing residue are not applicable to all the processes involved in semiconductor device manufacturing. For example, the first reference proposes a combination of etching gases to reduce the amount of residue in trench etching process. However, the combination of the etching gases proposed in the first reference is not applicable to other processes.
Therefore, it is still necessary to clean the chamber between different processes, when different processes are performed in a single chamber.